You must understand that the amount they are making now would be...

You must understand that the amount they are making now would be done in small batches primarily produced for their trials. They probably can only afford to give to the public what they have in excess. If/when the product is approved they will likely have to build a dedicated production facility to produce this drug in large batches. Supply is only unreliable now because large scale production is not PAR's focus at this point. From my experience working in a production engineering team I believe this is the reason for the unreliable supply. Hopefully your mum gets it soon.